Patent documents 1-3 are known as prior arts to form an insert member integrally with a parison when performing the blow molding of the parison.
A structure is disclosed in patent document 1 in which an insert member is clamped between a clamping member and the tip of a sleeve when forming a hollow container from a parison by blow molding, the hollow container is made to extend at the time of forming outwardly from the inside of the insert member, then the insert member is formed integrally with the hollow container, after this, the hollow member is ejected from the mold by the hydraulic cylinder.
It is disclosed in patent document 2 that to insert an insert member into the inside of the parison unitarily, the parison is pushed to the insert member from one side by a press-board and is unified by the driving of a hydraulic cylinder after the insert member is received in a pipe-shaped parison.
It is disclosed in patent document 3 that to form an installation flange by injection molding on the outer side of a parison unitarily a part of the blow-molding mold is used as a mold for injection molding when forming a parison by blow molding.